diff --git a/setup.py b/setup.py
index bca48d7..068ae25 100644
--- a/setup.py
+++ b/setup.py
@@ -17,7 +17,7 @@ numpy_include_dir = numpy.get_include()
 pykdtree = Extension(
     'utils.libkdtree.pykdtree.kdtree',
     sources=[
-        'utils/libkdtree/pykdtree/kdtree.c',
+        'utils/libkdtree/pykdtree/kdtree.pyx',
         'utils/libkdtree/pykdtree/_kdtree_core.c'
     ],
     language='c',